Open Surgical and Endovascular Management of Ruptured Abdominal Aortic Aneurysm

Crucial Diagnostic Triad

Pain, syncope, and a known or palpable AAA form a crucial diagnostic triad. If a patient has all three elements, he or she should be considered to have a presumptive diagnosis of an RAAA. If open surgical treatment is planned, such a patient should be taken immediately to the operating room and prepared for operation. No further diagnostic evaluation is necessary. Although an occasional patient will have another catastrophic problem, most of these patients require a laparotomy anyhow. The only exceptions are an acute myocardial infarction and pancreatitis. The former can be suspected because of EKG findings, the latter because of a high hematocrit and an elevated amylase.

The history of syncope is usually a manifestation of hypovolemia if cardiac courses can be excluded. The known AAA may be confirmed by history or the presence of a palpable pulsatile mass on physical examination. Although the pain element of the triad is usually in the mid-abdomen or back, it may be in the chest, the lower abdomen, the flank, or the groin. These unusual locations are caused by the pressure of the hematoma, which may not be centrally located and therefore producing unusual pain patterns. One example would be flank and groin pain mimicking a renal or ureteral stone. Another would be left lower quadrant pain and a mass mimicking diverticulitis.

If a patient has only two elements of the triad, further emergent diagnostic studies with ultrasound or computed tomography (CT) scanning are justified. However, a member of the surgical team should be with the patient during these urgent studies in case hemodynamic collapse occurs. The main purpose of these studies is usually to confirm the presence of an AAA, although occasionally blood can be seen outside the wall of the AAA or other important information can be provided.

Other Diagnoses That Can Be Mimicked by a Ruptured Abdominal Aortic Aneurysm

These diagnoses include most commonly a ureteral stone or diverticulitis. Other intraabdominal acute entities such as a perforated ulcer, a small bowel problem, or a pancreatic lesion can be mimicked by an RAAA and its associated hypovolemic shock and abdominal pain. Finally, an RAAA may present as a myocardial infarction with lower chest pain and nonspecific EKG changes because of the hypovolemic shock. One of the aspects of an RAAA that can contribute to this diagnostic confusion is the variable time course of the process depending on the variable containment of the rupture by adjacent structures. Another is the variable location of the rupture site and its associated hematoma.

Strategies in Planning Operative Treatment

When the diagnosis of an RAAA is presumed (three elements of the triad) or confirmed if two elements are present initially, a decision can be made to proceed with operative treatment. Although the patient should be taken immediately to the operating room, other elements or strategies in the treatment are important. The team must be assembled. This includes junior and senior surgeons, nurses, and anesthesiologists. Because these RAAA emergencies often occur at night or on weekends, assembling the team needed to treat them can take some time and organization. However, most operative procedures should not begin and the patient should not be anesthetized until all members of the team are present. While the team is gathering, lines and nasogastric and bladder tubes can be placed, instruments set up, and the abdomen prepared and draped. Only when all personnel are present should the patient be anesthetized because circulatory collapse is prone to occur when anesthesia removes the sympathetic compensation, which maintains the circulation in the hypovolemic state. Only if the patient's circulation collapses completely should a junior member of the team begin the operation before the whole team is fully assembled and operative preparations are completed. The strategic principle should be to rapidly get the patient to the operating room, but then proceed deliberately and only anesthetize the patient and begin the operation when everyone and everything is set up and in place.

One final strategy that is as effective in OR management as it is in endovascular treatment, is the use of hypotensive hemostasis or restricted fluid resuscitation. This means that bleeding is limited by allowing the patient to be hypotensive throughout the pre- and intraoperative phases of treatment. This will be discussed in greater detail in the endovascular treatment section.

Key Technical Points for Open Repair of Ruptured Abdominal Aortic Aneurysms

Once the abdomen is opened through a short midline incision, the base of the mesentery is inspected, and if blood is seen, the diagnosis of rupture is confirmed. The incision is then extended from xiphoid to pubis.

If the area of the infrarenal neck of the AAA is involved with hematoma, supraceliac aortic control should be obtained as shown in Figs. 43.1A–H . This is done without direct vision by tearing the lesser omentum with a finger ( Fig. 43.1A ). This exposes the retroperitoneum above the celiac axis and pancreas ( Fig. 43.1B ). Then, using the gloved index finger and its nail, the posterior peritoneum over the diaphragmatic crura is torn as indicated by the line in Fig. 43.1C and the fingertip pushed through the muscle fibers until the periadventitial space of the aorta is encountered ( Fig. 43.1D ). Then the finger bluntly dissects medially and laterally in the same plane creating a potential space on both sides of the aorta ( Figs. 43.1E–G ). Then two fingers are placed in the potential space and pulled caudally ( Fig. 43.1G ). A large covered DeBakey clamp is then placed vertically above the fingers into the space to occlude the aorta ( Fig. 43.1H ). Only if the aorta is freed from the crural fibers anteriorly, medially, and laterally will the clamp be occlusive. It is also crucial to have a nasogastric tube in the esophagus during these maneuvers so that this structure can be identified and protected from injury.

Following placement of this clamp, it is essential to minimize the time of supraceliac aortic occlusion (15 to 20 minutes is tolerable) to minimize liver and gut ischemia. To do this, the anterior wall of the AAA is exposed in its most prominent portion away from all venous and other structures. The anterior wall of the AAA is incised and a finger is placed within the AAA sac to identify the aortic neck. This may be deviated sharply to the right, left, or anteriorly because of aortic tortuosity associated with AAAs. With a finger inside to identify the position of the neck, it can gently be dissected bluntly from adjacent structures in the periadventitial plane without injuring major veins. Once dissected anteriorly, medially, and laterally, an infrarenal aortic clamp can be placed and the suprarenal clamp removed.

The iliac arteries can then be identified from without and clamped with gently placed atraumatic clamps. If they cannot be easily identified by palpation from without, they can be identified from within the lumen by a finger within the AAA sac. Clamps can then be placed on them without further dissection or with minimal dissection.

Clots are then removed from the interior of the AAA. Bleeding lumbar and any other branches are identified and controlled with sutures from within. A prosthetic graft is sutured in place from within the lumen of the AAA. The posterior walls of the aortic and iliac arteries should never be dissected, to prevent damage to other vascular structures. The posterior walls of the aorta and iliac arteries should not be transected, to avoid injuries to adherent major veins and minimize bleeding from other vascular structures.

Although it is controversial, heparin should be administered as soon as aortic clamp control is obtained. All dissection should be minimized in these RAAA repairs to minimize injury to other structures and blood vessels, the position of which can be distorted by the AAA and the hematoma. Otherwise, the repair should be as much like a standard AAA repair as possible. Care should be taken to monitor and treat hypothermia and coagulation defects. Finally, care should be taken to diagnose and treat abdominal compartment syndrome as detailed in the endovascular section later in this chapter.

History

Endovascular repair of an RAAA was first performed successfully by Marin et al. on April 21, 1994. Another case was first reported by Yusuf et al. in 1994. Since then, many centers have employed endovascular aneurysm repair (EVAR) to treat RAAAs, with varying results. Several groups have developed standardized systems of management in the RAAA setting, have used EVAR whenever possible, and have achieved good results with EVAR. In contrast, other authors have used EVAR for RAAAs more selectively and have reported no better results with EVAR than with traditional OR.

On the basis of these many reports, it is reasonable to say that the comparative efficacy of EVAR and OR for RAAAs is controversial, and some have advocated randomized, prospective, comparative trials of the two treatment methods with this entity. Three such randomized controlled trials (RCTs) were recently published and presented their results: the AJAX or Amsterdam (Dutch) trial, the ECAR or French trial, and the IMPROVE or UK trial. All three trials concluded that 30-day mortality outcomes after EVAR for RAAA are no better than those after OR. However, all three of these trials have serious flaws that render their results and conclusions misleading. These flaws are summarized in a recent publication. Because these RCTs are potentially misleading, the comparative efficacy of EVAR and OR in the RAAA setting remains controversial. We and many others believe that other evidence supports the superiority of EVAR when it can be performed. This view is also supported by a two-center study from Zurich, Switzerland and Orebro, Sweden in which all 70 RAAA patients seen over a 2-year period were treated by EVAR, although 24% required a chimney graft or other adjunct. The 30-day mortality for all these patients was only 24% and the turn-down rate for these RAAA patients was a remarkably low 4%.

In this chapter, we summarize other reasons that support the superiority of EVAR for RAAAs when the anatomy is suitable and suitable facilities, equipment, and skills are available.